1. Field of the Invention
This invention relates to pumpable water-containing surfactant concentrates containing alkyl and/or alkenyl oligoglycosides and betaine surfactants, to a process for their production and to their use for the production of surface-active formulations.
2. Statement of Related Art
Alkyl oligoglycosides, more particularly alkyl oligoglucosides, are nonionic surfactants which are acquiring increasing significance by virtue of their excellent detergent properties and their high ecotoxicological compatibility. The production and use of these substances have been described just recently in a number of synoptic articles, of which the articles by H. Hensen in Skin Care Forum, 1, (October 1992), D. Balzer and N. Ripke in Seifen-Ole-Fette-Wachse 118, 894 (1992) and B. Brancq in Seifen-Ole-Fette-Wachse 118 905 (1992) are cited as examples.
In some respects, however, the use of alkyl oligoglucosides is attended by problems. For example, it is not possible to produce pumpable water-containing concentrates with a solids content above 40% by weight without the sugar component undergoing partial decomposition in the course of the concentration process. The glycosides share this property with most anionic surfactants which form a viscous gel phase above an active substance content of around 35% by weight. In addition, alkyl oligoglucosides tend to crystallize during storage at low temperatures which significantly complicates their subsequent use.
The use of alkyl glucosides together with amphoteric or zwitterionic surfactants of the betaine type in surface-active formulations is known in principle from the prior art.
Mixtures of--albeit short-chain--alkyl glucosides and alkyl amido-betaines or imidazolinium betaines were disclosed for the first time in an article by G. Proserpio et al. in Rivista Italiana 56, 567 (1974). EP-A 0 075 994 (Procter & Gamble) discloses combinations of alkyl glucosides with amine oxides, unsaturated soaps, water-soluble builders and selected anionic surfactants. In addition, the mixtures may contain amphoteric surfactants, for example betaines of the 6-(N-dodecylbenzyl-N,N-dimethylammonium)-hexanoate type. Liquid soaps and foam baths containing alkyl glucosides, betaines and amine oxides are known from U.S. Pat. No. 4,668,422 (Henkel Corp.). EP-A 0 250 181 (Helene Curtis) relates to liquid detergents containing alkyl glucosides, anionic surfactants and selected amphoteric surfactants of betaine structure. EP-A 0 341 071 (Unilever) discloses surfactant combinations containing alkyl glucosides, alkyl sulfates, betaines and/or amine oxides and optionally alkanolamides. Manual dishwashing detergents containing alkyl glucosides, fatty alcohol sulfates, fatty alcohol ether sulfates and betaines are known from EP-A 0 513 138, DE-A1 4 234 487 and DE-A1 4 311 114 (all Henkel KGaA). EP-A 0 453 238 (Unilever) describes mild shampoos based on alkyl glucosides, anionic surfactants and betaines. Finally, EP-A 0 508 507 (Berol Nobel) relates to liquid detergents containing alkyl glucosides, anionic surfactants and selected amphoteric surfactants of betaine structure. However, these documents all relate to dilute water-containing surfactant mixtures or formulations and not to concentrates.
In EP-A2 0 353 580 (Th. Goldschmidt), it is proposed to prepare concentrated, flowable, water-containing solutions of betaines optionally containing lower aliphatic alcohols by carrying out the quaternization reaction in aqueous or aqueous/alcoholic solution in the presence of nonionic surfactants in such a quantity that the resulting solution has a nonionic surfactant content of, preferably, 3 to 20% by weight. Suitable nonionic surfactants for this purpose are, above all, fatty acid polyethylene oxide esters. In addition, it is known from DE-A1 4 305 083 (Henkel KGaA) that the quaternization of amines can be carried out in the absence of water and organic solvents, even in the presence of fatty alcohol polyglycol ethers.
There is a need in the market for concentrated surfactant mixtures based on alkyl and/or alkenyl oligoglucosides which are flowable and pumpable, despite a solids content above 30% by weight and preferably from around 40 to 50% by weight, and show a significantly reduced tendency towards crystallization, i.e. improved stability in storage. Since surfactant compounds of the type in question are mainly used in the cosmetics field, skin-cosmetic or father dermatological compatibility is also of paramount importance.
Surfactant concentrates are a particularly convenient commercial formulation for manufacturers and users alike because they have been minimized in regard to their water content and hence incur lower transportation and storage costs. Nevertheless, it is desirable that surfactant concentrates should have a sufficiently high viscosity for use in the end products, which are of course heavily diluted and have a solids content of 20 to 30% by weight, and should be readily thickenable using known additives.
Accordingly, the complex problem addressed by the present invention was to provide pumpable water-containing surfactant concentrates with high dermatological compatibility based on alkyl and/or alkenyl oligoglycosides which would be distinguished by high stability in storage, would have a Brookfield viscosity of at most 10,000 mpa.s and a solids content of 30 to 50% by weight and would readily lend themselves to thickening to a viscosity of at least 2,000 mPa.s on incorporation in cosmetic formulations with a water content of at least 50% by weight.